Orthodontics has been widely adapted in clinics to straighten or align teeth of a patient. The traditional method is to adhere brackets onto the teeth and run elastic wires through the bracket slots and provide the driving force, however, lingual orthodontics has been recognized and received wide interest since the 1970's. Lingual orthodontics involves bonding the bracket on the inner tooth surface instead of the labial tooth surface, which will not affect the appearance of the patient nor interfere with the closure of the lips. Meanwhile, the white stain caused by decalcification on the labial enamel of the tooth surface is avoided since the etching agent is not used. Also, it is easier for a doctor to observe the tooth position and shape from the lingual side during the treatment.
Currently, the brackets used for lingual orthodontics are off-the-shelf products which are manufactured as a single sized product. As such, the brackets have low adaptability for individual teeth. Because of the complicated appearance of the tooth lingual surface, smaller brackets are generally adapted for better adherence. The gap between the bracket and the teeth is filled up with dental adhesive. If there is more curvature on the tooth surface, more adhesive is needed, resulting in detachment of the bracket from the tooth surface. Comparing to labial orthodontics, lingual have more variable profile and require more matching brackets.
The major disadvantage of the lingual orthodontics is the stimulation of tongue. The tongue is one of the most sensitive organs in human body, which participates in frequent activities such as pronunciation and swallowing. Lingual brackets will deprive part of the room for the tongue and even cause pain by stimulating the edge of the tongue. In order to eliminate these side effects, manufacturing minute and fine lingual brackets has become the trend of development.
Rapid prototyping has been experimentally utilized in the manufacturing of lingual brackets. The general method is to firstly create a wax mold for the bracket through 3D-printing techniques, then fuse the mold and cast. There is no limitation for the brackets produced by this method and the individually customized manufacture is achievable. However, the process is intricate which involves multiple steps and long periods. Selective laser melting technique is an emerging and rapidly maturing prototyping technique and it has been utilized in the medical field. It can be used to directly manufacture lingual brackets which is usually composed of metal materials such as dental gold alloy or titanium alloys.
The existing manufacturing method of lingual brackets is standardized which can hardly satisfy the personal need of the patients, causing side effects on the treatment and resulting in heavy burden for the patients.